When producing metal parts having a circumferential wall, that is closed in peripheral direction, a flat ribbon material may continuously be transformed into a closed shape. To this end, the two lateral edges are combined around a longitudinal axis, and are interconnected by a welding seam. From the emerging tubular piece, the desired sections of circumferential wall, tubular jackets, are dissevered. The tubular jackets may be used as parts of a pipe or may be further processed into the respectively desired parts.
Widely used are cans made from sheet steel for which the jacket has a longitudinal welding seam. The bottom and/or the upper closure are attached to the can jacket. WO2005/000498 A1 discloses embodiments of can bodies with a can jacket made of sheet material. A bottom or an upper closing part is attached by way of laser welding to the can jacket.
Under the term of “can body”, one should understand every receptacle, in particular aerosol cans or beverage cans, but also collapsible tubes and intermediate products in the shape of a receptacle.
Known embodiments have a longitudinal can seam for closing the can jacket formed in the manner of a butt seam. For this, the edge regions on the side, which are to be joined, are guided along respectively one guide face, wherein these guide faces are oriented toward each other and extend over the complete length of the seam. So that the end faces of thin edge regions meet precisely, both edge regions are held against the partial guide faces. An exact meeting of the end faces of the two edge regions can be ensured by moving at least one edge region along the partial guide face toward the other edge region until they make contact. Once these regions are pushed together, the welding operation can be carried out.
So that no guide surfaces of the processing device need be arranged inside the can jacket, partial surfaces on the inside of the can jacket are used as guide faces. Welding of the longitudinal seam is carried out on a flat-pressed can jacket. In the welding-seam region between the two guide faces, a recess leading away from the edge regions to be joined and/or a region projecting outward from the jacket is formed, so that a connection to the guide faces is avoided during the welding operation. The adjoining, level partial surfaces are connected via curved regions.
So that no cracks or undesirable bulges are created in radial direction on the can jacket during the expanding of the flat-pressed can jacket, a form having a small radius of curvature but without folds is used in the flat-pressed state. The can jacket is essentially flat-pressed between the regions of curvature, so that a purposeful pressing together in at least one curvature region ensures the pressing together of the end faces during the welding operation.
The seam can be formed with the aid of different welding techniques, wherein a laser-welded seam is preferred. The flat material thus should comprise at least one metal seam that can be welded with a laser. In most cases, sheet steel materials are used which have good deformation characteristics and can be purchased with the desired thickness.
If necessary, the can jacket sections can be cut with a saw from the strip material, for which a saw blade or a saw belt moves along with the produced can tube during the sawing operation. The at least one cutting device is retracted following the cutting of a can tube section. Owing to the short sections and/or the small can heights, known cutting devices have disadvantages because they cannot cut and move back quickly. A further disadvantage of the known cutting devices is that particularly during the cutting of thin-walled tubes, there is danger of deformation and thus jamming. In addition, known cutting methods create shavings which would require further cleaning steps and/or create problems during the following can production stages.
According to references WO2005/000498 A1 and DE 1 452 556, a quick and clean cutting operation is ensured if the flat-pressed can jacket-strip material with pre-notched curved regions is moved along on a support, which can cooperate with a cutting edge. As soon as the desired length of the tube section is advanced, the cutting edge is moved in a cutting motion through the adjoining wall regions of the tube. The disadvantage of this cutting solution is the need for prenotching before welding the longitudinal seam and precise cutting aligned with the prenotched cuts after welding.